1. Field of the Invention
This invention relates to polymeric modifying agents having temperature-dependent properties.
2. Introduction to the Invention
It is known to control the rate of a chemical reaction by providing a reactant, a catalyst or other active agent in a modified form such that the availability of the active agent depends upon some external factor. For example, the active agent can be encapsulated by a protective shell which at least partly prevents access to the active agent. When release of the active agent or an increase in its concentration is desired, the shell is removed, or the shell is subjected to a treatment which does not destroy its physical integrity (i.e. the shell retains its shape and is not free to flow during the treatment), but which increases the rate at which the active agent can permeate through the shell. Removal of the shell can be effected, for example, by means of heat, solvent, or ultrasonic waves. A change in the permeation rate can, for example, be effected by using a shell having temperature-dependent permeability and by changing the ambient temperature; for further details of particularly useful temperature-dependent systems of this kind, reference may be made, for example, to commonly assigned U.S. Pat. No. 4,830,855 (Stewart), U.S. Pat. No. 5,129,180 (Stewart) and U.S. Pat. No. 5,254,354 (Stewart), the disclosures of which are incorporated herein by reference for all purposes.
It is also known to use so-called xe2x80x9clatent hardenersxe2x80x9d or xe2x80x9clatent curing agentsxe2x80x9d, optionally in conjunction with xe2x80x9clatent acceleratorsxe2x80x9d. These xe2x80x9clatentxe2x80x9d compounds can be mixed with the other ingredients for a crosslinked resin, e.g. an epoxy resin or a polyurethane, to give compositions which are relatively stable at room temperature but which cure rapidly when heated to an elevated temperature, e.g. 160xc2x0 C. or more. Systems of this kind are disclosed for example in U.S. Pat. No. 4,349,651 (Smith), U.S. Pat. No. 4,358,571 (Kaufman et al), U.S. Pat. No. 4,420,605 (Kaufman), U.S. Pat. No. 4,430,445 (Miyake), U.S. Pat. No. 4,659,779 (Bagga et al), U.S. Pat. No. 4,689,388 (Hirai et al), U.S. Pat. No. 4,701,378 (Bagga et al), U.S. Pat. No. 4,742,148 (Lee et al) and U.S. Pat. No. 4,933,392 (Andrews et al), and European Patent Publication No. 362787 A2 (Henkel), the disclosures of which are incorporated herein for all purposes.
Many attempts have been made to develop systems which are stable for extended periods at storage temperatures, but which will cure rapidly when heated to give crosslinked polymers having desired properties. However, only limited success has been achieved.
It is also known to prepare polymers containing reactive moieties which will react with other materials under appropriate conditions. For example, in the materials often referred to as xe2x80x9cpolymer-supported catalystsxe2x80x9d, the reactive moiety is one which provides a catalytic function. Reference may be made, for example, to Encyclopedia of Polymer Science and Engineering, Vol 2, pages 702-729, the disclosure of which is incorporated herein by reference for all purposes.
We have now discovered, in accordance with this invention, that greatly improved results can be achieved through the use of polymeric materials which comprise (i) a crystalline polymeric ingredient which melts and flows over a relatively small temperature range and (ii) an active chemical ingredient which promotes or inhibits a chemical reaction of a matrix. Such materials are referred to herein as xe2x80x9cmodifying agentsxe2x80x9d. We have found that when such a modifying agent, in solid form, is in contact with the matrix (e.g. as solid particles dispersed in the matrix), the polymeric ingredient restricts the contact between the matrix and the active chemical ingredient. On the other hand, when the modifying agent is heated to the melting point of the crystalline polymeric ingredient, the modifying agent melts and flows, and as a result there is a rapid increase in the extent to which the matrix is contacted by the active chemical ingredient. A similar increase can also be achieved by other treatments, either alone or in conjunction with heating (either simultaneously or sequentially), which cause the modifying agent to lose its physical integrity, so that the polymeric ingredient and the active chemical ingredient are free to disperse into the matrix, preferably so that they become substantially uniformly distributed thereon. Such other treatments include for example, one or more of (a) addition of a solvent, (b) exposure to electromagnetic radiation, including visible and ultraviolet light, or to ultrasonic radiation, or (c) increasing or decreasing the pH. In some cases there is a chemical bond between the polymeric and active chemical ingredients; in other cases, the active chemical ingredient is merely associated with, preferably dispersed in, the polymeric ingredient.
The active chemical ingredient is one which promotes or inhibits a chemical reaction of the matrix under selected conditions. The selected conditions can result directly from the treatment which increases the availability of the active chemical ingredient, or they can involve some further change (e.g. a change in temperature, pressure, pH or radiation, or the addition of a solvent or a reactant) that does not substantially reduce the extent to which the matrix is contacted by the active chemical ingredient. The active chemical ingredient can be (1) a catalytic ingredient (i.e. an ingredient which (a) reacts chemically with an ingredient of the matrix and is thereafter regenerated or converted into another compound, or (b) reacts chemically with a material which is adjacent to or absorbed into the matrix and is thereafter regenerated or converted into another compound, and in either case does not form a permanent chemical bond with an ingredient of the matrix); or (2) a reactive ingredient (i.e. one which reacts chemically, and forms a permanent chemical bond, with an ingredient of the matrix, and is not regenerated); or (3) an inhibiting ingredient (i.e. one which reduces the rate of a chemical reaction of the matrix, optionally by itself reacting preferentially with a material, e.g. oxygen, which would otherwise react with the matrix).
In particularly preferred embodiments of the invention, the crystalline polymeric ingredient is a side chain crystallizable (SCC) polymer. SCC polymers generally contain side chains comprising substituted or unsubstituted n-alkyl groups of 6 to 50, usually 12 to 50, carbon atoms, derived, for example, from one or more n-alkyl acrylates or methacrylates. The melting point of an SCC polymer is in large measure controlled by the number of carbon atoms in the n-alkyl group or groups and is not (as in most other polymers) heavily dependent on the molecular weight of the polymer or on the presence of other comonomer units (e.g. derived from acrylic acid, acrylonitrile or an unsubstituted or substituted lower alkyl acrylate). Furthermore, SCC polymers generally melt over a small temperature range, e.g. less than 10xc2x0 C. As a result, it is possible to select an SCC polymer which will cause the modifying agent to melt over a narrow and predetermined range, thus making a sharp change in the extent to which the active chemical ingredient contacts the matrix.
As explained in detail below, a number of different factors influence the extent and the speed of the change in the extent to which the active chemical ingredient contacts the matrix. These factors include (1) the form of the modifying agent (in particular the size of the particles thereof, when, as is preferred, the modifying agent is in the form of particles dispersed in the matrix), (2) whether or not there is a chemical bond between the polymeric ingredient and the active chemical ingredient, and if there is a chemical bond, the nature and the strength of the bond between the polymeric moiety and the active chemical moiety (which may be a covalent, ionic, mixed covalent-ionic, or ligand-attached bond, preferably a covalent bond), (3) the crystallinity of the crystalline ingredient and the temperature range over which it melts (which is preferably less than 10xc2x0 C. between onset of melting and peak on a DSC curve), (4) the extent and rapidity of the temperature change or other treatment which is carried out in order to promote (or inhibit) the chemical reaction of the matrix, (5) the presence of coadditives, and (6) the presence of enhancing groups on one or both of the matrix and the modifying agent. Preferably, the combination of these factors results in an increase in the effective concentration of the chemical moiety by a factor of at least 500, particularly at least 1000, especially at least 2,000, with substantially greater increases, e.g. at least 3,000, being obtainable in many cases.
The surface of the solid particles or film of the modifying agent will normally be directly contacted by the matrix material. However, the invention includes the possibility that the modifying agent will be at least partly encapsulated by a material which can be removed before or after the modifying agent is activated, e.g. a polymeric coating having a melting point below To.
The temperature-sensitive modifying agent used in the present invention
(a) comprises
(i) a polymeric ingredient which comprises a crystalline polymeric moiety having an onset of melting temperature To and a peak melting temperature Tp such that Tpxe2x88x92To is less than Tp0.7, preferably less than Tp0.6, and
(ii) an active chemical ingredient which, when in contact with a matrix material under selected conditions, promotes or inhibits a chemical reaction of the matrix material, and
(b) is in the form of a solid which, when exposed to a change in a variable selected from temperature, concentration of a solvent, electromagnetic radiation, ultrasonic radiation, and pH, undergoes a physical change which causes the modifying agent to lose its physical integrity and increases the extent to which the matrix material is contacted by the active chemical ingredient.
In a first preferred aspect, this invention provides a composition which comprises
(1) a matrix material; and
(2) distributed in the matrix material, or adjacent to the matrix material, a modifying agent as defined above which undergoes a said physical change when it is subjected, while it is in contact with the matrix material, to a said change in a variable, and which is preferably in the form of
(i) solid particles which are distributed in the matrix material, and which have one or more of the following characteristics
(a) an average particle size of 0.1 to 150 microns,
(b) a polymeric ingredient having a heat of fusion of at least 20 J/g, and
(c) a polymeric ingredient in which the crystalline polymeric moiety is a side chain crystalline polymer, or
(ii) a film which is in contact with the matrix material.
In a second preferred aspect, the invention provides a method of making a chemical compound, especially a polymer, which comprises
(A) subjecting a composition according to the first preferred aspect of the invention to a said change in a variable; and
(B) simultaneously with step (A), or after step (A), subjecting the matrix material and the modifying agent in contact therewith to conditions which cause a chemical reaction of the matrix material.
Many of the chemical compounds and products which can be prepared by the second preferred aspect of the invention are themselves novel. Thus, many of the compounds which result when the modifying agent reacts with the matrix material are novel when there is a chemical bond between the polymeric and active ingredients. Other products which can be prepared in accordance with the present invention, although known as chemical compounds in some products, are not known as other useful products, e.g. as foams, which are easily prepared by this invention. These novel compounds and products are part of the present invention. For example, in a third preferred aspect, this invention provides a copolymer which comprises
(A) first polymeric blocks which comprise a polymeric moiety comprising a crystalline polymeric moiety having an onset of melting temperature To and a peak melting temperature Tp such that Tpxe2x88x92To is less than Tp0.7, and
(B) second polymeric blocks which are different from the first polymeric blocks, the copolymer having at least one of the following characteristics
(1) the first polymeric blocks are derived from a novel modifying agent as defined below as the fifth preferred aspect of the invention;
(2) the crystalline polymeric moiety in the first polymeric blocks has a heat of fusion of at least 20 J/g and/or is a side chain crystalline polymeric moiety, and the copolymer is in the form of a foam, an electrically insulating coating on a conductor, a coating on a printed circuit board, a resist on a substrate which is to be plated or etched, an epoxy graphite composite, or a powder coating; and
(3) the crystalline polymeric moiety in the first polymeric blocks has a heat of fusion of at least 20 J/g and/or is a side chain crystalline polymeric moiety, and the polymer is crosslinked, preferably thermoset so that it does not flow when heated; and
In another example, in a fourth preferred aspect, this invention provides a product which comprises
(A) a first polymer which is a side chain crystalline polymer having an onset of melting temperature To and a peak melting temperature Tp such that Tpxe2x88x92To is less than Tp0.7, preferably less than Tp0.6, and
(B) a second polymer which is different from the first polymer, which is thermoset so that it does not flow when heated, and which provides a continuous phase in which the first polymer is distributed.
The compositions and methods of the first and second preferred aspects of the invention offer a number of important advantages over known compositions. Especially when the polymeric and active chemical ingredients of the modifier are chemically bonded to each other, particularly through a covalent bond having a bond strength of at least 10 Kcal/mole, the compositions can have improved storage stability such that they can be stored in larger containers and used partially and from time to time; that they may not need to be sealed against the ingress of moisture, etc.; that they may not need to be transported and stored under cooled conditions; and that they can be pumped from a storage area to a manufacturing area. Even when there is no chemical bond, or only a weak chemical bond, between the polymeric and active chemical ingredients of the modifier, and as a result the increase in stability is relatively small, this can be very valuable, for example in reaction injection molding (RIM) processes. The compositions can also contain other ingredients, for example additives which reduce the viscosity of the composition, surface active agents, including wetting agents, compatibilizers, and melt flow promoting agents.
Some of the temperature-sensitive modifying agents used in this invention are novel compounds and as such are part of the present invention. Furthermore, many of the temperature-sensitive modifying agents, even though known as chemical compounds for other purposes, are novel in forms, e.g. particles or thin films, which are particularly suitable for use in this invention, and in such forms are part of the present invention. For example, a fifth preferred aspect of this invention provides a temperature-sensitive modifying agent as defined above which has one or both of the following characteristics
(1) the active chemical ingredient is chemically bonded to the polymeric ingredient and is a catalytic moiety comprising a metal or an enzyme, and
(2) the crystalline polymeric ingredient has a heat of fusion of at least 20 J/g and/or is a side chain crystalline polymeric moiety, and the modifying agent is in the form of particles having an average diameter of 0.1 to 150, particularly 0.1 to 50, microns.
In a sixth preferred aspect, this invention provides a method of making a temperature-sensitive modifying agent which comprises
(i) a polymeric moiety which comprises a crystalline polymeric moiety having an onset of melting temperature To and a peak melting temperature Tp such that Tpxe2x88x92To is less than Tp0.7; and
(ii) a catalytic moiety which is bonded to the polymeric moiety through a bond having a strength of at least 10 Kcal/mole;
said method comprising
(I) copolymerizing
(a) a first monomeric component which comprises one or more monomers which can be polymerized to form a crystalline polymeric moiety having an onset of melting temperature To and a peak melting temperature Tp such that Tpxe2x88x92To is less than Tp0.7, and
(b) a second monomeric component which can be copolymerized with the first component and which comprises one or more monomers containing an active chemical moiety which (i) does not react during the copolymerization and (ii) contains a metal or an enzyme and can catalyze a reaction of a matrix;
(II)
(A) providing a polymer which comprises
(i) a crystalline polymeric moiety having an onset of melting temperature To and a peak melting temperature Tp such that Tpxe2x88x92To is less than Tp0.7, and
(ii) at least one reactive group P; and
(B) reacting the polymer provided in step (A) with a component which contains at least one reactive group T which will react with the group P and at least one active chemical moiety which (i) does not react during the reaction and (ii) contains a metal or an enzyme and can catalyze a reaction of a matrix; or
(III)
(A) providing a polymer which contains at least one reactive group Q and a plurality of catalytic moieties which contain a metal or an enzyme and can catalyze a reaction of a matrix, and
(B) reacting the polymer provided in step A with a component which (i) contains at least one reactive group V which will react with the group Q and (ii) after the reaction, provides a crystalline polymeric moiety having an onset of melting temperature To and a peak melting temperature Tp such that Tpxe2x88x92To is less than Tp0.7; or
(IV)
(A) providing a polymer which contains a plurality of reactive groups R, which may be the same or different, and
(B) reacting the polymer provided in step A with a first component which (1) contains at least one reactive group W which will react with the group R and (ii) after the reaction, provides a crystalline polymeric moiety having an onset of melting temperature To and a peak melting temperature Tp such that Tpxe2x88x92To is less than Tp0.7, and with a second component which contains at least one reactive group X which will react with the group R and at least one active chemical moiety which (i) does not react during the reaction and (ii) contain a metal or an enzyme and can catalyze a reaction of a matrix.
In a seventh preferred aspect, this invention provides a method of making a temperature-sensitive modifying agent as defined above in which the polymeric ingredient has a heat of fusion of at least 20 J/g and/or contains a side chain crystalline polymeric moiety, which method comprises forming the modifying agent into particles having an average diameter of 0.1 to 150 microns, e.g. by milling the solid modifying agent, or by spray drying or otherwise forming into particles (a) a solution of the modifying agent or (b) the molten modifying agent; or, in a different procedure which results in particles of the active ingredient coated by the polymeric ingredient,
(A) forming the active chemical ingredient into particles having an average diameter of 0.1 to 150 microns, and
(B) forming the polymeric ingredient into a coating around the particles prepared in step (A).
In one such method, the molten modifying agent can be mixed with a suitable heated matrix and then cooled so that the modifying agent solidifies in the form of particles dispersed in the matrix.